Fuse



V on firing in the Patented Feb. 13, 1951 UNITED STATES PATENT OFFICE FUSE Harry J. Nichols, New York, N. Y. Application May 7, 1943, Serial No. 486,056

3 Claims. (Cl. 102-80) present particular difficulties because of their very small size, the great accelerating and rotary certain in action.

simple in design and operation, (2) easy to manufacture and load, (3) free from deterioration in storage, (4) safe in handling and using, and

Accordingly, the principal objects of the present invention are to meet all of the complex special and general requirements specified above by a fuse simple in construction and adapted to low cost manufacture in large quantities.

forces to which the parts are subjected in firing and in flight, and the heavy forces encountered at impact. Because of the desire to obtain maximum penetration of armor, a nose fuse, which would necessitate weakening the front end of the projectile, is undesirable and a base fuse which avoids this limitation is to be preferred. However, the space available for a base fuse is very limited.

Because of the extreme force of set-back than 75,000 g, the detonator of some fuses may be exploded by concussion. This makes a detonator-safe feature highly desirable. Because the bore of the gun deteriorates rapidly due to the high rate of fire of automatic cannon, the possibility of coppering and other obstructions occurring in the barrel must be considered. This makes a bore-safe feature highly desirable, and since the cannon may be fired through protective Weather-seals, it is desirable that the fuse not be completely armed until the projectile has travelled some distance beyond the muzzle of the gun. This is termed a muzzle-safe feature. Fuses of this class are subject to a projectile spin in flight exceeding 100,000 R. P. M. and in order to insure certain arming and reliable firing action, it is essential that the moving elements be dynamically balanced with re-- spect to the axis of rotation of the projectilein flight, which. is also the axis of the fuse. Moreover, unless the rotor is dynamically balanced, the flight stability .of a small projectile will be impaired. The fuse detonation of relatively insensitive explosives.

And since the projectile may strike the target In addition to the special requirements recited above, fuses of this class are required to be (1) Other objects will be in part obvious from the annexed drawings and in part hereinafter indicated in connection with the following analysis of the invention.

In the drawings forming part of this disclosure, like characters of reference denote corresponding parts throughout the several views, in'

which Fig. 1 shows in enlarged longitudinal crosssection a base detonating fuse designed for gun, often amounting to more mm. projectiles illustrating one embodiment of the invention, the mechanism being shown in unarmed position, that is, normal, safe position;

Fig. 2 shows the same fuse in as in Fig. 1, the mechanism being shown in armed position as in flight;

Fig. 2a shows the same fuse as in Fig. 2, but in cross-section at plane aa of Fig. 2;

Fig. 3 is similar to Fig. 2, but is rotated 90 and shows the mechanism in exploding position on ,cross-section at plane 33 of Fig. 5;

impact with the target;

Fig. 3a is an end view of Fig. 3;

Fig. 4 shows the rotor inperspective presentation to make its form evident;

Fig. 5 shows in longitudinal cross-section another embodiment of the invention incorporating a short delay device, the mechanism being shown in unarmed position;

Fig. 5a shows the fuse of Fig. 5 in transverse Fig. 6 shows the same fuse as Fig. 5 in the same view, but with the mechanism in armed position, as in flight;

Fig. 7 shows enlarged ,the shape of the anti creep ring 3 and the rotor retainer ring 9 shown must contain a relatively large detonator capable of producing high order in Figs. 5 and 6; and

Fig. 8 shows in perspective the assembly of the rotor housing, rotor, and. the retainer ring to illustrate the relations of these parts.

Referring now to these drawings, and particularly to Fig. 1, the main structural member of the fuse is the casing or body !'of cylindrical form and with external screw threads for assembly to the projectile (not shown);

an inner axial bore Ic housing the percussion firing element 2 and a the same section" The forward portion 3 combined safety and anti-creep element 3, and an axial counterbore or chamber lb containing the rotor housing 4 which is secured in the body, preferably by crimping as shown.

The rotor housing 4 has a rectangular cross-slot in which is supported edgewise on a support disc 1 a centrifugal rotor 5, shown in equatorial section in Fig. 1, in the form of a doubly truncated sphere with two equal and parallel faces. (See Fig. 4:.) This rotor has a diametral bore adapted to receive a detonator 6 (preferably sealed in a moisture-proof capsule as shown), and one or more small tapered holes 571. located on the equator at an angle of say 50 to the aXis of the detonator hole. The firing point 2p of the firing element 2 extends into one of the tapered holes to retain the rotor 5 so that the detonator 6 is normally positioned obliquely. In this, the unarmed position, the detonator is masked from the firing point (which lies safe in the exploding position) and is in safe relation to the concentrator recess M in the housing 4.

The centrifugal rotor is centro-symmetric, that is, it is symmetrical with respect to its center of mass, being of the type generally disclosed in my Patent No. 2,446,019, dated July 2'7, 1948. Consequently, it is statically balanced with respect to any axis passing through its center. In form it resembles a sphere cut away symmetrically from opposite sides to leave the central portion with two equal and parallel fiat sides in which diametral channels 50 are cut. (See Figs. 2a and 4.) These channels extend substantially parallel to the axis ofthe detonator hole and leave two symmetrical lands or circular segments 5s on each side, which segments upon rotation of the fuse about its axis on firing produce a double torquecouple tending to rotate the rotor so as to bring the detonator into alignment with the axis of the fuse. (See Fig. 2.) There is also a similar minor torque due to the difference in specific gravity of the detonator and the rotor metal which it displaces, but this minor torque is generally ineffective to turn the rotor if there is any eccentricity of rotation such as occurs in flight due to the yaw of the projectile. The torque-couples due to the four segments tend automatically to compensate for minor eccentricity, such as that due to yaw of the projectile in flight. Hence the segments may be considered to produce the effective torque which turns the detonator into armed position as shown in Fig. 2.

As the rotor lies in the housing in unarmed position with its center of gravity on the axis of the fuse body and with the detonator extending obliquely as in Fig. 1, the rotor is substantially statically balanced, and having virtually no tendency to rotate, the rotor is easily retained in unarmed position by the firing point. But upon withdrawal of the firing point and rotation of the fuse in flight, due to the effect of the torquecouples of the segments the rotor is dynamically unbalanced and turns into armed position with the detonator in alignment with the firing point as shown in Fig. 2. Once in this position, the torque-couples cancel each other, maintaining the rotor in a dynamically stable condition with the detonator in alignment with the fuse axis. Thus, when the rotor turns the detonator into armed position in response to centrifugal force, the same force positively maintains the rotor in armed position against displacement by any extraneous force or forces. The need for locking detents and the like, typical of prior art, is thus avoided, and

4 the rotor is in itself self-locking in armed position.

Referring again to Fig. l, the safety element 3, which in this embodiment is a spring-like helix of wire with the turns wound against each other, surrounds the lower part of the firing pin and bears against a small enlargement or bead 2b formed on the shank of the firing element. The end coils of the helix are somewhat enlarged in diameter so as to be a light force fit in the bore of the body, thereby enabling the helix to function as an anti-creep device as hereinafter described. Thus, the helix 3 normally maintains the firing element in safe position with the firing point securely entered into one of the tapered holes 5h in the rotor, this being the same position relative to the fuse body which the firing element occupies in the exploding position as shown in Fig. 3. Since the rotor normally has no particular tendency to turn out of armed position, the firing point suffices to hold the rotor in unarmed position against accidental displacement, even when subjected to jolting and jumbling tests.

Thus, it is evident that the invention provides a fuse arming mechanism of extreme simplicity but of great versatility and security.

Referring now to the figures in sequence, the operation of the fuse mechanism is as follows:

In Fig. l the parts are shown in the normal position of rest in which they are assembled, and the detonator 6 is maintained in safe position as described above. On firing in a gun, the condition of the fuse becomes that shown in Fig. 2 in which set-back at firing in the gun has caused the firing element to slide downwards to the bottom of the bore (despite the resistance of the helix 3 to the entry of the bead 2b) and thereafter, when the projectile has travelled some distance beyond the muzzle of the gun, the rotor 5 turns the detonator 6 into armed position as shown. It is to be noted that although centrifugal force acts on the rotor while in the bore I of the gun, such force is negligible compared to the force of set-back, and the rotor does not have the power nor time to rotate until after the projectile has travelled well beyond the muzzle of the gun. As the projectile emerges from the gun and strikes the atmosphere, the helix, being tight in its bore, restrains the firing element from plunging forward and thus acts as an anti-creep device. Hence in the event the detonator were exploded by the shock of concussion on firing, or should the projectile encounter an obstacle inside or immediately outside the gun, the detonator would be in safe position and incapable of exploding the projectile.

It will be evident from the above description of the functioning of the fuse mechanism during firing from the gun that the detonator does not become armed until the projectile has passed well beyond the muzzle of the gun, hence the fuse is detonator-safe, bore-safe, and muzzle-- safe.

During flight the fuse continues in the condition shown in Fig. 2 until an obstacle is encountered, whereupon the firing element plunges forward due to the force of percussion (see Fig. 3), stabbing and exploding the detonator which in turn instantly explodes the projectile charge.

It will be evident that the burst of the projectile will occur quickly but not quite instantly upon impact with a substantial obstacle, this type of use action being technically termed nondelay action, and producing a burst within a few inches of the point of impact. For the most destructive action against some types of targets, as for example bombersprovided with multiple armour plates, it is desirable to'delay the burst for a distance of a few feet, technically termed short-delay action; -The fuse of the invention can readily be adapted to provide such shortdelay action and one embodiment of theinvention for that purpose will now be described.

Referring now to Fig. 5, the fuse mechanism there shown includes 'all'the elements of the prior type (some of these elementsbeing slightly modified-in form) and two additional elements, namely, a primer 8 and a rotor retainer ring 9. The similar elements in the two types are similarly numbered, and attention is now directed to the modifications and additions.

Since only moderate sensitivity is desired in fuses for use against relatively heavy structures such as bombers, the firing element 2 now takes the form of a ball 2', and the combined safety and anti-creep element 3 the form of a single expansion ring 3 assembled in the bore of the fuse body I after the ball 2' hasbeen put in place.

To obtain a short delay, aprimer 8 is inserted in the explosive train ahead of detonator 5. The

expansive force of the ring 3' normally suifices to hold ball 2' from exploding contact with primer 8, and in flight acts as an'anti-creep device to.

maintain ball 2 in the rearward position, thus ensuring an adequate stroke of ball 2' with primer 6 on impact with the target. certain firing action, it being well known that primers are reliably fired by a sharp blow, rather than merely by pressure.

Since the primer 8 prevents co-action between the firing element and rotor to maintain the rotor in unarmed position as in the prior type, a separate retainer element, in the form of a split compression ring 9, hereafter termed the retainer ring, is provided.

Referring now to Figs. 5, 6 and 8, the cylindrical diameter of rotor housing 4 isslightly reduced below the head to provide a clearance between the housing and the inside counterbore of the body as can be clearly seen in Figs. 5 and 6.

Further, a shallow groove is turned in the pee riphery of the reduced cylindrical portion of housing t, and a corresponding groove 5g is turned around rotor s transverse to its main diameter and at an angle of about to the axis of the detonator (see Fig. 4). When the rotor is assembled into the housing in the proper position, the ring 9 is slipped over both to retain the rotor in proper relation to the housing (see Figs. 5 and 3). role of safety retainer for the rotor, which role was played by the firing point in the prior embodiment.

The operation of the second embodiment is as follows: In Fig. 5 the parts are shown in the position in which they are assembled, and the detonator 6 is maintained in safe position as described above. On firing in a gun, set-back causes the retainer ring 9 to slide downwards as viewed to the position shown in Fig. 6, thereby freeing the rotor. After the projectile has left the muzzle of the gun some distance, the rotor turns into armed position and the parts are in the armed position shown in Fig. 6.

Upon impact with a substantial target the firing element, that is the ball 2', is projected forcibly forward by percussion force, carrying anti-creep ring 3' with it and exploding primer 8, which after a slight delay ignites detonator 6, which in turn detonates the explosive shell- The ring 9 therefore plays the 7 This promotes charge (not shown'i to burst the projectile. It

will be noted that the anti-creep ring 3' ensures that the ball will not move forward until a substantial obstacle is encountered. Thus the fuse defeatsthe purpose of so-called light burster plates positioned ahead of armor plate in some bomber constructions for the purpose of prematurely actuating the fuse, whereupon the armor plate can easily hold back any fragments from the burst projectile.

Without detailed analysis, it will be evident that as in the prior embodiment, this fuse with short-delay action is "fully detonator-safe, bore-safe and muzzle-safe, and that the addition of the delay featuredoes not violate the cardinal requirement of simplicity.

It should be evident from the foregoing that the invention provides novel and advantageous features in fuses, and that the invention as a whole, while simple in form, meets the complex general and special requirements for fuses of this class in a highly efiicient and practical manner.

I claim:

1. In a minor calibre base detonating fuse for 'said percussion element so as to engage said equatorial portion thereof and slidable in said bore for retaining said percussion element in safe position until impact with the target, a centrifugally actuated centro-symmetric round dynamically balanced rotor carrying a detonator rotatably mounted in said axial bore independently of and ahead of said percussion element in unarmed position with its center of gravity on the axis of said fuse body, and means normally in restraining engagement with said rotor and movable from such restraining engagement only by set-back force for retaining said rotor in unarmed position until said fuse is fired from a gun.

2. A centrifugally armable base detonating fuse for projectiles comprising, in combination, a onepiece cylindrical fuse body having a continuous forward chamber and rearward axial bore, a rotor housing member having a central slot mounted immovably in said chamber, a centrifugally armable and dynamically balanced centro-symmetric rotor of disc-like form supported edgewise in'said slot by non-pivotal means and having a diametral bore carrying a detonator normally retained in unarmed position at an angle to the axis of the fuse body, a safety element mounted in said chamber so as to retain said rotor in unarmed position and movable rearwardly by set-back to release said rotor for subsequent arming, a percussion firing element assembled axially slidable in said axial bore and having an equatorial portion, a combination safety and anticreep element assembled in said axial bore and engaging the equatorial portion of said firing element so as to prevent said firing element from moving from assembled position prior to firing in a gun and'from approaching said detonator prior to impact of the projectile with the target.

-3. The combination of claim 2, and of means Number Name Date for delaying the firing of said'detonator after im- 523,110 Dungan July 17, 1894 pact of the projectile with a. target. 1,292,505 Newell Jan. 28, 1919 HARRY J. NICHOLS. 1,311,104 Watson July 22, 1919 5 1,534,011 Watson Apr. 14, 1925 REFERENCES CITED 1,550,978 Lukens Aug. 25, 1925 The following references are of record in the 2,155,100 13, 1939 e of t t 2,392,430 Te1tsche1d Jan. 8, 1946 UNITED STATES PATENTS 1o FOREIGN PATENTS Number Name Date Number Country Date 320,210 Bennett June 16, 1885 15355 Great Britain v- 13, 1913 

